The program is evaluating apparent blood viscosity related parameters (blood viscosity at various rates of shear, hematocrit, red cell deformability, fluidity and size, degree of cellular aggregation, plasma viscosity and serum protein profile) as diagnostic and prognostic indices for diseases related to or produced by altered blood flow or circumstances arising from surgical procedures. The degree of correlation between the various parameters is being measured in order to develop the minimum set of measurements required for a hemorheological profile on blood samples. Subjects and patients are being divided into groups based on sex, disease and procedures, for statistical analysis which will provide a readily accessible summary of all the measurements of each individual and also a means of surveying how well the various parameters discriminate between the groups of subjects and patients. The classification of normal subject is based upon the blood chemistry profile and hematological indices of the blood coupled with assessment of the clinical status of the volunteer. The non-surgical patients (myeloma and peripheral vascular disease) show a significantly higher apparent blood viscosity over the entire range of shear rates compared with the control group regardless of the effects of variation in hematocrit. Women on oral contraceptives displayed a similar small but significant increase in apparent whole blood viscosity over the female control group not on contraceptives. The knee replacement patients show marked increases in ESR and fibrinogen coupled with significant elevations in apparent blood viscosity for hematocrits equivalent to the preoperative values. By the eighth day post surgery the parameters are beginning to return towards the preoperative values. Precise knowledge of the nature of the interactions between blood viscosity related factors should enable the hemorheological profile to be used for monitoring the course of diseases, improving diagnostic tests and as an aid in devising therapeutic manipulations to produce selective modification of deviant rheological parameters.